1. Field of the Invention
The present invention relates to an apparatus for preventing malfunction of a remote controller, an electronic device and a remote control transmitter provided with a function of preventing malfunction of a remote controller, and a method for preventing malfunction of a remote controller, and more particularly relates to the art of preventing malfunction when a plurality of electronic devices connected to a common control bus are controlled by using remote controllers.
2. Description of the Prior Art
In general, various types of electronic devices such as a CD player, a DVD player, an MD player, a cassette deck, a radio tuner, a television receiver, and a navigation apparatus are accompanied by a remote controller, and operations of these electronic devices are controlled remotely. Recently, there are increasing cases where a plurality of electronic devices is provided at home or in a vehicle, and thus, the number of electronic devices to be remotely controlled is increasing.
For example, head units which can reproduce Audio Visual (AV) sources such as a CD, a DVD, an MD, a cassette tape, a radio and the like, a television receiver, and a navigation apparatus are installed in the vehicle passenger cabin. These electronic devices are respectively accompanied by a dedicated remote controller, and are also respectively provided with a light reception unit for an infrared remote control signal. In one case, a television receiver and a navigation apparatus share one monitor, and a light reception unit is provided on the monitor thereof. In this case, a remote controller may be shared.
In this situation, when one wishes to control an electronic device, one should operate a remote controller, which is dedicated to the electronic device to be controlled, and is directed to a remote control light reception unit provided on the electronic device. However, it is considerably annoying to change the direction of the remote controller each time according to where the electronic device to be controlled is installed.
Especially in an environment where a plurality of electronic devices may be installed in a small space such as a vehicle passenger cabin, it is necessary to install the electronic devices close to each other. In some cases, a remote control light reception unit of one electronic device is blocked by another electronic device, and thus, the remote control signal may not be properly received. Indeed, a monitor is often installed above a head unit installed in a console, and a remote control light reception unit of the head unit is often blocked by the monitor.
Conventionally, in order to solve this problem, there is a proposed system where a plurality of electronic devices provided with a remote control light reception unit are connected with each other through a common control bus, and the respective electronic devices communicate a remote control signal with each other (see, for example, Japanese Patent No. 2506969).
In this type of system, a remote control signal received by one electronic device using its own remote control light reception unit is transmitted to other electronic devices through the control bus. The remote control signal contains a code specifying an electronic device to be controlled, and thus, the electronic device specified by this code can operate in response to this remote control signal. In this way, as long as at least one of the plurality of remote control light reception units receives a remote control signal, all the electronic devices can receive this remote control signal, thereby increasing the capability of receiving a remote control signal.
According to the prior art described above, the respective electronic devices connected to the control bus may receive the same remote control signals both from its own remote control light reception unit and the control bus. Also, these respective electronic devices may receive a remote control signal either from its own remote control light reception unit or the control bus depending on conditions such as the direction of the remote controller, the intensity of the light, and the location of the remote control light reception unit. Consequently, the respective electronic devices carry out processing based on both the remote control signals received from the remote control light reception unit and the remote control signals received from other electronic devices through the control bus.
However, the remote control signal from the control bus is transmitted on the control bus after the remote control light reception unit of another electronic device receives the signal, and thus, is delayed with respect to the remote control signal received by its own remote control light reception unit. Especially, as a characteristic of the control bus, if the traffic is high on the control bus, a remote control signal cannot be transmitted immediately, possibly resulting in an increased delay. At the same time, remote control signals acquired from the same control bus may present an interval in the arrival depending on the transmission states of the respective electronic devices. For example, if a large amount of data is already present in a transmission buffer of the electronic device, it may take a long time before the remote control signal can be transmitted.
If the electronic device receives the remote control signals arriving respectively from its own remote control light reception unit and from the control bus with an interval between them in this way, the remote control is carried out twice (the system considers that the same operation is instructed twice) although these remote control signals are generated from an operation instructed only once.
As a result, for example, even if an operation of turning up a sound volume is instructed only once, the sound volume will be turned up by two steps. As for an operation of turning on/off the power supply or various functions, an operation instructed only once will be carried out twice, and consequently, even if a user intends to turn on the power supply, the power supply will be turned off immediately after it is turned on, for example. This phenomenon appears to be an apparent malfunction to the user.
To avoid such a malfunction, as shown in FIG. 8(a), it may be possible to employ a processing method such that a plurality of remote control signals received in a certain time period are considered to be the same remote control signal, and remote control signals received after the first remote control signal are disregarded.
It should be noted that the delay of the remote control signal arriving from the control bus changes depending on the traffic of the control bus and the transmission state of the electronic device on the sending side as described above, and thus, a long delay may be generated. In this case, if the time period in which all the received remote control signals are considered to be identical is set short, as shown in FIG. 8(b), the same remote control signal acquired from the control bus after a long delay may be considered as a different remote control signal, and the remote control signal arriving subsequently may be validated. Therefore, this certain time period must be set to a longer time period including a certain margin.
However, when the time period in which all the received remote control signals are considered to be the same is set too long, as shown in FIG. 8(c), although the user may actually operate the remote controller a plurality of times, the remote control signals corresponding to the subsequent operations are all considered as invalid, and only the first operation will be acknowledged. As a result, there is the problem that the user has an impression that the responsiveness of the remote controller is inferior, and thus, it is extremely difficult to operate the remote controller.